This invention relates to a printing plate mounting arrangement.
More particularly, the invention relates to an arrangement for facilitating the mounting of printing plates on the plate cylinder of an offset printing machine.
In offset printing machines the matter to be printed is contained on a printing plate which is mounted on, and rotates with, the plate cylinder of the machine. Therefore, whenever the matter to be printed is to be changed, the old printing plate must be removed and replaced by another one containing the new matter to be printed. Removal of the old plate presents no problem, because no particular care and certainly no precision is required. However, this is different when the new plate is being installed, since the plate must be so positioned that it is properly located on the plate cylinder; otherwise, mis-prints will result.
This requires a series of carefully executed operations on the part of the operator (or even several operators where large printing plates are to be handled). For example, the operator must hold the plate in exactly the right position during insertion of one of its edge portions into the retaining slot of the plate-cylinder plate-clamping rail. Care must be taken to assure properly precise positioning of the plate relative to the various abutments which are provided. Once the edge portion of the plate is properly and securely clamped, the printing machine is then operated in "creep" mode so that the slowly turning plate cylinder winds the plate up about its circumference.
A problem with this is that the printing plate can easily be damaged during such handling. If the damage is serious enough to be noted at once, the printing plate will have to be scrapped before printing even begins. If the damage is not so immediately noticeable (e.g. to the print face), the situation is even more annoying because as a rule some printing will have been done before the damage is discovered and the entire printing run up to discovery will then have to be discarded along with the printing plate. Moreover, the prior art manner of installing a new printing plate is physically demanding of the operator and is also rather slow, which latter factor is reflected in comparatively long machine down time.